Method for manufacturing the metal coated amorphous powder

ABSTRACT

A metal-coated amorphous powder having high toughness and plasticity is made by uniformly coating nano size metal on a powder surface through spray drying. The amorphous powder is added to a metallic salt solution and mixed. After mixing, the solution is spray dried. As the dried powder is heated, the salt is eliminated successively or at the same time to be reduced. The metal is a salt of any one of Cu, Nickel, Iron and Cobalt.

TECHNICAL FIELD AND PRIOR ART

The invention relates to the method for manufacturing amorphous powder, more particularly the method for producing the powder having high toughness and plasticity by uniformly coating some metal of nano size on the powder surface through spray drying.

As amorphous material has very excellent strength, wear resistance and Corrosion Proof etc comparing over the common metal, some flexible possibility for manufacturing the components to be applied for automobiles, electronics and sports looks very high. Therefore, A lot of studies to develop various types of amorphous powder with better performance are now under progress, and until now many different kinds of amorphous material composed of Al, Ni, Zr etc respectively have been developed.

However, such developed amorphous powder material has not yet been sufficiently applied to the industrial fields. This is because the characteristics for amorphous powder material itself have some shortcomings with very poor toughness and machinability resulting from poor plastic deformation and ductility of nearly zero different from the common metal material. Moreover, In case of manufacturing some precision components of the amorphous powder from powder metallurgy it may not achieve because some crystallization develops due to poor plasticity, high sintering temperature during sintering after forming.

Even though a lot of efforts to overcome such defects by improving some amorphous metal alloy compositions by means of the complex of amorphous and crystalline etc are being made, until now any clear methods for the improvement are not yet suggested. For example, there are some problems still available having some oversize over micro unit for the powder although it was manufactured by coating the copper on the amorphous powders through electro less plating.

OBJECT OF THE INVENTION

Accordingly, the invention is proposed to solve the problems for said amorphous material. The object is to provide the method of manufacturing the amorphous powder with both high strength and toughness by uniformly coating the metal of nano size on the surface of the amorphous powder through spray drying.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a flowchart of the manufacturing process for the invention.

FIG. 2 shows a scanning micrograph for the amorphous powder material according to the invention.

FIG. 3 shows a XRD graph for the powder material in FIG. 2.

FIG. 4 shows some scanning micrographs for the amorphous powder manufactured according to the invention, in which FIG. 4 a for overall powder and FIG. 4 b for powder surface are indicated respectively.

FIG. 5 shows a XRD graph for the powder as shown in FIG. 4.

FIG. 6 shows some scanning micrographs for other amorphous powder manufactured according to the invention, in which FIG. 6 a, overall powder, FIG. 6 b, a powder surface respectively.

FIG. 7 shows a graph comparing a relative density formed for the amorphous powder according to the invention with one of the prior arts.

SUMMARY OF THE INVENTION

To achieve said object the present invention provides to the method for manufacturing metal coated amorphous powder formed, wherein the method comprises the steps of mixing metal salt solution with amorphous powder to prepare mixture solution: spray-drying the mixture solution to obtain dried powder; and heating the dried powder to eliminate salt therefrom and to simultaneously be reduced.

Further, the invention may mix by adding some auxiliary substance such as caustic ammonium or caustic potash etc after adding amorphous powder to the metal solution during said mixing step.

Further, the invention may heat the dried powder to eliminate the salt therefrom, and the reduction of the powder is carried out.

The invention is fully described as the following:

FIG. 1 shows a general layout for the manufacture. First the amorphous powder and metal salt being used for the original material is prepared respectively.

The amorphous powders used as raw materials for the invention become the objects of all those including Nickel, Zirconium, Iron etc. These amorphous powders may be manufactured by some various processes such as milling method, melt spinning or gas injection process etc.

Further, said metal salt solution is a soluble salt form in the water as the main composition for each type of metal. It is desirable as said metal salt solution to choose one out those of Cu, Ni, Fe and Co. Cu salt composed of Cu as a main element is soluble in the water. For example, Copper Nitrate[Cu(NO₃)₂] or Copper Nitrate, Hydrate[Cu(NO₃)₂xH₂O] etc may be referred to. The quantity of metal composition of said metal salt solution may be determined depending on that trying to coat on the amorphous powder. For the quantity of the metal coating on the amorphous powder it is desirable to maintain below 30 wt %.

Further, the metal salt solution is used mixing the metal salt with distilled water and the quantity of amorphous powder added to the metal salt solution is to determined depending on that of the solution.

For the invention, it is desirable to manufacture the metal salt by adding and mixing a small amount of auxiliary substance for the purpose of increasing the solution viscosity to improve the adhesiveness between said amorphous powder and metal salt solution. For the auxiliary substances, Ammonium Hydroxide[NH₄OH] or Potassium Hydroxide[KOH] etc may be referred to. In case the viscosity of said metal salt solution is too high, much metal salt may be attached on the surface of the amorphous powder. However, adequate control of the viscosity is very critical due to the poor supply of the solution during spray-drying. Further, the metal content to be coated is different depending on the required material and may be adjusted by the metal salt concentration. Preferably, said auxiliary substance is added below 10 mol to the metal salt solution.

Thereafter, as FIG. 1 shows, solid amorphous powder and metal fluid salt solution are mixed for the solid and fluid to make a mixed slurry condition. Using a rotary type stirrer such as magnetic stirrer etc more effective mixing is obtained.

The metal salt coated amorphous powder is manufactured with the mixed slurry by using the spray dryer. Said spray dryer may apply a centrifugal spray or high pressure injection method etc.

Next, after the salt composition of the metal salt manufactured by the spray drying is eliminated from the coated amorphous powder, the reduction treatment thereof is performed. It also does not matter even though such salt elimination and reduction process are carried out at the same time. At this time, each temperature for the salt elimination and the reduction treatment should be maintained at the temperature range without any crystallization of amorphous powder.

For example, when heated under the atmosphere between the temperature of 300˜550° C. to eliminate the salt content, such process is realized by the reaction of oxygen and metal salt in the atmosphere. During the process, the metal is also partially oxidized.

Accordingly, after the salt is eliminated, for reducing the oxidized metal followed by being heated at the temperature range between 300˜550° C. in the reducible atmosphere and next being cooled, the amorphous powder coated thereon with metal powder of nano size is manufactured.

EXAMPLES

The invention is illustrated in more detail by reference to the following examples.

Example 1

The amorphous powder was manufactured through gas spray by melting Ni system ingot. The compositions of the manufactured powder were Ni: 52.7 wt %, Zr: 28.7 wt %, Ti: 13.6 wt %, Si: 1.3 wt % and Sn: 3.7 wt %. Further, as shown in FIG. 2 and FIG. 3, the size of said powder is below 100 μm, all of which are known to be amorphous.

Next, to manufacture the complex powder, the quantity of Copper Nitrate Salt[Cu(NO₃)₂3H₂O] corresponding to Cu 5 wt % was estimated and dissolved in the distilled water. And the viscosity up to a certain point enough to attach on the amorphous powder surface was to be obtained by adding the ammonia water of 1 mol to increase the viscosity of Cu salt solution.

After amorphous powder and Cu salt solution prepared in this way was mixed by a rotary stirrer for 30 minutes, the Cu salt coated powder was manufactured by operating a rotary spray dryer. At this time, the temperature inside the spray dryer between 125˜130° C. and the rotating speed of 15,000 rpm were maintained respectively.

Thereafter, it was heated for 1 hour at about 400° C. to eliminate the salt from Cu salt coated amorphous powder.

Next, a reduction treatment was performed by heating for 2 hours at about 500° C. under the pure hydrogen atmosphere to reduce the oxidized Cu.

FIG. 4 shows some scanning electronic micrographs for the Cu coated amorphous powder manufactured by said method. As shown in FIG. 4 a, very fine particle of nano size attached on the surface of the Cu coated amorphous powder can be seen. Further, By observing an enlarged micrograph as shown in FIG. 4 b, it could be verified that the Cu powder was coated uniformly on the amorphous powder surface with a comparatively defined size

FIG. 5 shows a XRD result verifying that the said powder manufactured consisted of amorphous powder and Cu. In the graph of FIG. 5, only pure Cu peak appears. This proves that pure Cu powder only exists by the normal reduction of the oxide after the processes of salt elimination and reduction. This also shows that the amorphous powder during the processing is not crystallized.

Example 2

To manufacture the amorphous powder containing 10 wt % of Cu, the amorphous powder by the same method as Example 1 was manufactured. After estimating the quantity for Copper Nitrate Salt[Cu(NO₃)₂?3H₂O], Cu solution was prepared by the same method, and the Cu salt coated powder was manufactured by means of spray drying process.

In Example 1, the salt elimination and reduction process were made separately, but in Example 2, it was heated at 500° C. under hydrogen atmosphere and cooled to carry out the salt elimination and reduction treatment at the same time.

FIG. 6 shows the powder forms prepared in this way, FIG. 6 a, overall powder, FIG. 6 b, the surface form respectively. It can be seen that the fine Cu powder of nano size is uniformly coated on the amorphous powder surface in FIG. 6 as FIG. 4. Further, the quantity of coated Cu powder used in case of Example 2 was twice more than that of Example 1. Therefore, it can be seen that more Cu powder than that of Example 1 is available on the surface of the amorphous powder

Example 3

The pure amorphous powder prepared as said Example 1 and the same method as said Example were applied to manufacture the amorphous powder coated up to max 20 wt % of Cu. Thereafter each powder was formed. The plasticity for each formed body prepared was measured. Then, the plastic condition was to be formed for 30 minutes at 500° C. without any crystallization of the amorphous and to obtain the formed body. Thereafter, the relative density for each formed body was measured.

FIG. 7 shows the relative plastic density for each formed body depending on Cu content. As shown in FIG. 7, the pure amorphous powder without any Cu coating indicates the relative density of 81%. However, when Cu is coated it can be seen that the plastic density increases gradually. Further, in case of the formed body manufactured with the 20% wt % coated amorphous powder, a high relative plastic density of about 95% can bee seen.

Example 4

The amorphous powder was prepared to manufacture the amorphous powder containing Ni of 5 wt % by applying the same method as Example 1. After estimating the quantity of Ni(NO₃)₂6H₂O, Ni salt solution was prepared. Ni salt coated powder was manufactured through the spray drying process.

As Example 1, the salt elimination and reduction was performed by each separate process. Then, the temperature for the salt elimination was maintained at higher 470° C. over than that of Example 1. The reduction treatment was carried out at 500° C. under the hydrogen atmosphere.

The manufactured powder form was similar as shown in FIG. 4. Fine Ni powder of nano size was uniformly coated on the amorphous powder surface.

ADVANTAGE OF THE INVENTION

According to the invention as said, the metal/amorphous powder is obtainable by coating uniformly the metal of nano size on the surface of the amorphous powder applying the spray drying process to improve poor toughness, one of defects for each kind of amorphous material.

Further, the manufactured powder in this way is different from the powder manufactured by the non-electrolytic plating. Therefore, nano size metal coated amorphous powder may contribute to improve the plasticity and sintering property considerably. 

1. A method of manufacturing amorphous powder comprising the steps of mixing metal salt solution with amorphous powder to prepare a mixture solution; spray-drying said mixture solution to obtain dried powder; and heating said dried powder to eliminate salt therefrom and to simultaneously be reduced.
 2. The method according to claim 1, wherein said metal salt solution comprise any one of Cu, Ni, Fe and Co.
 3. The method according to claim 2, wherein said metal salt solution contains an element selected from the group consisting of 30% wt or less of Cu, Ni, Fe and Co.
 4. The method according to claim 1, wherein ammonium hydroxide or caustic potash is added as an auxiliary substance after adding the amorphous powder to the metal salt solution in said mixing step.
 5. The method according to claim 4, wherein said auxiliary substance of 10 moles or less is added to the metal salt solution.
 6. The method according to claim 1, wherein said dried powder is heated to eliminate the salt therefrom, and then the reduction of the powder is carried out. 